Alumina-metal oxide dehydrogenation catalyst and its preparation



May 12, 1953 E. w. PITZER ,63 ,45

ALUMINA-METAL OXIDE DEHYDROGENATION CATALYST AND ITS PREPARATION Filed June 14, 1948 2 Sheets-Sheet 2 U 45 El '0. CATALYST A l- :1: PER PASS YIELD OF 40 g CATALY$T B NCAHa +C4H6 x as 970 990 |0|0 I030 I050 I070 I090 |||0 TEMPERATURE, F

FIG. 4

I I r-' a a o I K I O 1' U 2.5 .9 I I z Q 2.0 g Ld 5 I 5 8 I,

I CATALYST B7 CATALYST 0.5 so 40 so so TOTAL CONVERSION, wT.%

, INVENTOR.

5w. PITZER BY )Z M A 7' TORNE VS Patented May 12, 1953 ALUMINA-METAL OXIDE ,DEHYDROGENA TION CATALYST AND ITS PREPARATION Emory W. Pitzer, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Application June 14, 1948, Serial No. 32,834

19 Claims.

This invention pertains to a process for the manufacture of hydrocarbon conversion catalysts and to the catalysts made by the -process. The Invention also relates to hydrocarbon conversion processes .which involve the changing of the carbon-to-hydrogen ratio of the hydrocarbons. A specific aspect of the invention is concerned with the dehydrogenation of Cz-Cio hydrocarbons.

Various hydrocarbons, particularly those con taining at least two and not more than ten carbon atoms'per molecule, must frequentlybe dehydrogenated to produce more unsaturated materials suitable for various purposes in the chemical and petroleum industries. Such reactions include dehydrogenation of butane to produce butylenes, dehydrogenation of butylenes to produce butadiene, dehydrogenation of other paraffins to produce the corresponding olefins, dehydrogenation of olefins to produce the corresponding diolefins, dehydrogenation of naphthenes to produce aromatics, and dehydrocyclization of aliphatic hydrocarbons to produce aromatic hydrocarbons. Conversely, it is frequently desirable to effect hydrogenation of un saturated material to' produce more saturated products, for example, hydrogenation of aromatic hydrocarbons to produce cyclo-aliphatic hydrocarbons, andhydrogenation of petroleum'frac- I dons-containing olefinic materials to effect saturation thereof.

The catalyst of the invention encompassescomposite metal oxide catalysts of chromia alumina'and chromia-beryllia-alumina and similar'composites. At the present time, catalysts comprising alumina in combination with at least one of the oxides of metals of the left-hand colunm of group 6 such as Cr, Mo, W, and U, and V of group of the periodic table, together with a promoter such as beryllium oxide, are recognized as the best composite catalysts for catalytic dehydrogenation of hydrocarbons such as n'-butane. For. example, a particularly effective catalytic composition for dehydrogenating paraffin hydro carbons is found in athree-component catalyst, consisting of about 50% alumina, 40% chromia, and 10% beryllia. Other proportions of these constituents are also effective in hydrocarbonder' hydrogenation processes. A conventional method of preparing such composites is the impregnation of a substantially dehydrated alumina pellet with salt solutions of the other metals followed by the conversion of the metal salts to the metal oxides. Sometimes finely divided aluminum oxide is first impregnated with the metal salts followed by decomposition and conversion to the metal oxides and is thereafter pelleted into finely divided com- 2 catalyst up to this time have'been made by coprecipita'ting the'metal oxides from solutions of their salts so: as to obtain a composite gel consisting ofthe metal oxides in intimate contact in a homogeneous gel. Various other methods of preparing dehydrogenation catalysts have been devised, none of which produce catalysts superior to the co -precipitated gel catalysts just referred to. While the co-precipitated gel catalysts are superior dehydrogenation catalysts, they are comparatively expensive because of the complicated and time-consuming methods required in their preparation.

The present invention encompasses the use of the catalysts described herein in processes for adding hydrogen to, or taking hydrogen from,

hydrocarbons. They are'particularly effective in.

dehydrogenating normal butane to normal butenes, cycle-hexane to benzene, ethyl benzene to styrene, and analogous reactions involving homologs of these materials. These catalysts may be used to advantage in the dehydrogenation of any dehydrogenatable hydrocarbon, under conditions of temperature, pressure, and reaction time within conventional ranges such as 900 to 1300 F; up to- 500 p. s.- i. gs, and 0.5 to! 5 liquid volumes of charge pe'r'volume of catalyst per hour, and are especially -'advantageous; when treating hydrocarbons having at least two and not more than 10 carbon atoms per molecule.

It is a principal object of the present invention to-provide a comparatively simple and economical' method of manufacturing a highly efficient dehydrogenation catalyst which has unusually long life, a high total conversion, and low coke formation; It is also an object of the invention to provide improveddehydrogenation catalysts. A further object of the invention is to provide an improved process for dehydroe 'genating' hydrocarbons, particularly paraifin hydrocarbons, including'the dehydrogenation of n-butaneto butylenes and butadiene. Other I posite's which are superior dehydrogenation catalysts to co-precipitated gel composites of the same: metal oxide concentration has been found. This method comprises digesting a mixture of the oxides selected for the composition with nitric acid for, an extendedperlod of time, followed by heating the digested mixture until it is dry and hard and converting any nitrates formed to oxides, thereafter comminuting the digested and I dried'mixture, forming a mixture with water or posit'es; The most effective dehydrogenation I with-Ste'rotex (hydrogenated corn oil) or other suitable binder, and forming the mixture into pellets by any conventional method or" pelleting. If desired, the catalyst composite can be utilized in finely divided form after the comminuting step, for example. in; the fluidi-zed'catalyst tech.- nique. It'is preferred -to form a. homogeneous mixture of the oxides in finely divided form before digesting in nitric acid. A suitable method is to grind the oxides in any typed-grinding,

equipment until the material-.passes. a. lQtl-meslm screen, and preferably a 325-mesh screen. Sulficient nitric acid of 20 to 70% conceni'nzation should be added soas to at least thoroughly .wet;

the mixed oxides. Usually about two or three times the weight of the mixedaoxidesis suitable.

but acid weight between and 5 times the weight of the mixed oxides will produce. superior catalysts. The digestionmay be carried on under totall refiux oriaeid may be added periodically in orderxtormaintai'n a suitableamount of-acidin in an amount between? and 3. times theweight of the finished catalyst improves the-activity of the' catalyst all; cases; more particularly so when the starting :material is a...lower oxide of-one orimo-i'e metals of the left-hand .colunmcf group Sand ct. vanadimm The ammonium nitratecan be addedxat anytime duringthe digestion "period; but is; preferable: toincorporate it at an earlystage inthe digestion. or in the mixed oxidesbefore the-digestion is initiated.

thepreparation; of, an"; alumina-chromia composite by themethod of the. invention, suitable dehydrogenation catalysts: scan be prepared with any reasonable proportionsrofi these constituents, but an amount otchromium oxide in the range of-w'to by weight oi-the final compositeis preferred in that such composites-are more efiective in=- dehydrogenation: reactions; However, evenin' compositions: outside of the: preferred range; the method :oi: the.:rinventionproduces catalysts which" are more..-azctive than catalysts ofsimilar' "concentratiorriofi'lchromium :and' 3,111? minum" oxides: -made-rby other: known methods. usingoth'er group 16 metal oxides and/or vanadium in -the composite, similartproportions arepreferred; The addition uncertain-stabilizers or promoters to the icompositewcatalysts.may'be madewith eiiectlve resuits; A conventional com-'- positee comprises the ;oxides of aluminum, chroand beryllium. .v Sometimes magnesium .is substitutedsforaberyllium withasimilarly improved results; When. including beryllium oxide the compcsztepitmay be. included-man amount between 1 and by weight of the finished catalyst,: preferably fito 19%- byweigh"- When incorporating "magnesium oxide-rm: the .catalyst composite; similar amountsumaybeused. It is contemplated that. the balance oi the catalyst is aruminum; oxide. Hence, the; alumina taken with'th'e" group 6 metaloxides and/or. vanadium composite catalyst makewup. at least.85 weight per cent of theeatalyst composite. While the catalyst hashthusiar been described as ineluding-only one metal oxide from groups 5 and 6-. as:.enumerated hereinabove,- the. inclusion of morethan: one otthese metal oxides inranamount 4 between 10 and 70% by weight of the finished catalyst is within the scope of the invention.

The following examples showing the above method of manufacturing dehydrogenation catalyst: offispecific compositions and "dehydrogenationprocesses inthe presence of theseicatalysts are set forth in order to provide a clearer understanding of the invention. Certain obvious modifications of .theprocedures set forth may be made without'departingirom the scope and spirit of the invention. The proportions of catalyst componentsrin .the' following examples and elsewhereahereinuar'e'given in parts by weight, or alternatively inweight per cent.

EXAMPLE I CATALYST A 40CI2O310B6O50A12O3 (mixed oxides digested in; mam acid) .'-Ohromium 1 trioxide, beryllium and. alumimim': oxide are stirred and: boiled icir 46 :underztotal reflux with 70 percent nitriciacid equivalent-to about three times-=the weight at the oxides. After-digestion, the mixheated to:.'780 F: in 30% minutes and-kept atlthat: temperature :for v15 .hourszheated material, which is: dark brown andzhasx anaiap parent density-of about 0.2 gram-per: ccais mixed with w per centzwater and 5' per cent Sterotex, ground hammer rriilltto pass a-.l.00-mesh sieve and "pilled; Sterotex is :removedlfrommhe pillsbyheatingithem in'a stream of air .to 1000115. initthours andrkeepingthem at that. temperature 01121 hours:

EXAMZPLEII CATALYST B51 40GrzQa-el0BeO-50AlzOs' cQ recipitatedIP- e drated chromium,..beryllium, and aluminum .ni trates @941; 36 9, andlfiimfigrams,respectively) are dissolved andodiluted with distilled water to about 0.2!E-molar concentration a glassr container. Concentrated ammonium hydroxide (5'1 per cent) isadded slowly. with vigorous stirring sothat the metal hydroxides precipitate .andthe pHZ oi the mixture is LA-in about 2..15 hours. The mixture isfiltered immediatelyin vBuchner:funnels and. the filter-cake-is dried for" 52.5 hours at about 200 F. Ammonium nitrate is decomposed: and themetal hydroxides .areconverted to oxides-by heatinggthedry residue to 750? E. in .a round-e bottom. flask. in 30 minutesandmaintaining at that; temperatureiorZA hours- The heated residuesis exposed to air :for 24: hours and absorbs 12.5 per;cent moisture.v It wasqmixed ,withb percent Sterotem ground. to. pass a lOO-mesh sieve, pill-ed. andcalcined.

CATALYST G- 40CrzOa--1OBeO -50 AlzOs (mechanically-. mixed owidesl .-Ghromic oxide,- beryllium oxidaqand aluminum oxide are'mix'ed' for-'5 minutescinva WaringBlend'or, mixed with S'per'cent Stem sex foranad ciitional 2 minutes, madeinto'pil-ls. heatedin a stream of air to 1000 F. i113 hours, and kept. at that temperature for 21 hours to re-'- mo-ve Sterotex;

EXAMPLE'IV CATALYST D 40Cr2Q'ae1flBe0e50AlzOa. (mixed oxides digested in -water --Chromic oxide, beryllium oxide, and aluminum oxide are stirred and boiled for. 62 hours total refluxwith water equivalent to-,about.twice-- the. weight of the oxides. After.

digestion the mixture is heated to-750 F. in-3 hours and kept at that temperature for=44 hours. The heatedmaterial, which is green, ,is mixed with 5v per cent-Sterotex, ground in a hammer mill to pass a--100-mesh screen,- and. pilled. Sterotex is removed from 17116131115 by heating them in a stream of air to 1000 F. in- 3-hours and :keeping them at that temperature for 19 hours.

1 r EXAMPLEV GATALYsT E 40CrzOs-10BsO-50Alz0a (mixed oxides digested in .dcetieyacidL-Chromiirni trioxide, beryllium oxide, and aluminum oxide are stirred and boiled for 45 hours under total reflux with glacial acetic acid equivalent to about twice the weight of the oxides. After digestion the mixture is'heated to 750 F. in 8 hours and kept at that temperature for 48 hours. The heated material, which is dark brown, is mixed with 10 per cent 'Sterotex, ground in, a hammer mill to pass a l-mesh sieve,and pill ed. Sterotexis removed from the bills by heating them in a stream of air to 1000" F. in 3"hour's' and keeping them at that temperature for 21 hours. Crushing strength of the pills before and after Sterotex removal is 4.2 and 6.2 pounds, respectively.

EXAMPLE VI v CATALYST F v 40C1203-10BBO-50A1z03 (mixed oxides digested in nitric acid) .-Chromic oxide, beryllium oxide, and aluminum oxide are boiled with 70 per cent nitric acid equivalent to about three times the weight of the oxidesfor 43 hours, during which the liquid level is kept constant by periodic addition of fresh acid. After digestion the mixture is heatedto 780 F..in 4.5 hours and kept at that temperatureior 24 hours. The. top layer of the calcined material is a black mass and the bottom layer, whichis used for this catalyst, is a greenish- .brown, finely divided powder. The powder is mixed with 2 :per cent water and per cent Sterotex, ground in a hammer mill to pass a ,100-mesh sieve, and pilled. Sterotex is removed from the ills by heating them in a stream of air to 1000 F. in 3 hours andkeeping them at that temperature for 21 hours:

' EXAMPLE VI I .CATALYsT G 40Ci203-1OB6O-50A12O3 (mixed Oxides digested in nitric acid) .Chromic oxide, beryllium oxide,

and aluminum oxide are stirred and boiled for 47 hours under total reflux with '70 per cent nitric acid equivalent to about three times the weight of the oxides. After digestion the mixture is heated to 750 F. in 36 hours and kept at that temperaturefor 36 "hours. Theheated material, which is green and'has a low apparent density, is mixed with per cent water and 5 percent Sterotex, ground in a hammer millto pass a lOO-meshsive, and pilled. Sterotex is removed from the pills by'heating them in a stream of air 5 oxide, beryllium oxide, andaluminumoxide are stirred and boiled for 44 hours under total reflux with ammonium nitrate equivalent to about twice the weight of the oxides and '70 per cent nitric acid equivalent to about three times-the weight of the oxides. After digestion the mixture is heated to 800 F. in 24 hours, kept at that temperature for 128 hours, and heated at 550 F. for 36 hours. The heated material, which is dark brown, is mixed with 10 per cent water and 1 0 per centSterotex, ground in a hammer mill .to pass a -mesh sieve, and pilled. Sterotexis removed from the pills by heating them in; a stream of air to 1000 F. in 3 hours and keeping them at that temperature for 21 hours.

Catalyst B is selected from a large number. 0 co-precipitated gel type catalysts of this composition made by varying techniques and represents the best catalyst of this type available at the present time. Similarly, Catalyst A represents the best acid digested catalyst made according to the present invention. The various catalysts, except Catalyst B, of the examples are compared by eiTecting the dehydrogenation of a technical grade n-butane stream in the presence of each of the catalysts under substantially identical'opcrating conditions and diiierent temperatures ranging from 1000 to 1100 F. at a space velocity of 750 v./v./hr..and at atmospheric pressure. A1- ternate dehydrogenation and regeneration periods of 60 and 56 minutes, respectively, are used. The following table gives the per pass yield of N-C4Hs and C4H6 in weight per cent as obtained in the tests. 4

TABLE I Temperatures, F. Catalyst The data in the following table show a comparison between the activity and the life of Catalysts A and B obtained by dehydrogenating nbutane at atmospheric pressure, a temperature of 1030 F., butane and regeneration gas space velocities of 750 and 3,000 v./v./hr. (S'I'Phrespectively, and dehydrogenation and regeneration periods of one hour each. The percentageof 8 day activity after 44 days use is also shown.

TABLE II For Pass Yield of Percentage NC4HaP+G4H, Weight of 3-day ercen ac 1V1 y Catalyst after i 1 days use 0 days 8 days 44 days A 44. 0 37.0 36. 2 97.8 B 40.0 38.3 31. 7 s2. 8

Figure 1 of the drawings shows a comparison between the ultimate yield of NC4H8+C4H6 effected by Catalysts A and Bin the'dehydrogena- ,tion of n-butane' at various temperatures using a butane space velocity of 750 v./v./hr. at atmospheric pressure. Figure 2 shows the total con: version effected by Catalysts A and B under-the same, operating conditions as used in obtaining the data in Figure 1. similarly, ,Figuretjshow's aesonts 7 the per-pass "yield of N -04m: +CHa effected with Catalysts andB. Figure 4 shows the weight per :cent of conversion to coke in proportion to ithetotal conversion in weight per :cent effected by Catalysts A :and 13 under thesame operating conditions es'Figure'l.

It'isclear from the data of l'fable Ithat'Catalyst A made by I the processof "the invention'isa superior catalyst to Catalysts C,- E,- and E. Catald'sts and D are substantially equal in activity, the "former consisting of a simple pelleted 'mixtime of the oxideswhile the latter consists of a comparable mixture digested with water prior' to pelleting. Apparently, digesting the mixed oxides with water has little .efiect-onthe activity :of the resulting catalyst; Digesting the mixed oxides with'acetio acid (zCatalyst E) eiiect :some immonement in catalyst activity but does :not onhanoecatalystactiflty comparably to nitric acid sitgestien.

A comparison of theactivityo1 Catalyst Fwith that of :Catalyst G (both catalysts haylingibeen IHHIdBiZbY digesting the mixed oxides, including with M639 indicates that the :aidditionof lacidvtor'the mixture during digestion :is an improvement over digesting under total reflux whenutilizing the :sesqui-oxide as thechromium oxidieestartmg material.

"The data for (Catalyst .I-l, prepared in the same :CatalystsG, except "for the addition of NH4NO3 to the digestion mixture, show the imefieo'ted by ll'HtNOz treatment during digestion. improvement is also effected when digesting the oxides in the presence of NH4NO3 where the starting chromium oxide is the trioxide but the improvement is less marked.

The experimental data presented. in Table II clearly show the superiority of-Catalyst A mover Catalyst-B in initial activity and in continued high activity over a-sub-stantial period-oi time (catalyst life) When digesting the mixed oxides containing 011203 as the :source of chromia, the digestion with nitric acid must proceed at least 1-0 hours before the characteristic 'reddishjbrown .color of hexavalent chromium appears and further immovement in the catalyst is effected by extendingthe digestion period. When starting the {Ii- .gestion with C1203 as the source of chromi-a, jimmovement of :the :catalyst obtains-from as little a as one. 'lrour of digestion but .greaterimproyement is efiected by increasing the'digestion period. The tel-lowing table shows theryield-oi NC4Hs+C4Hs in weightpericentiof the butane feed, whensdehydrogenatingm-Ebntaneaat 11060" atmospheric pressure, and a space velocity of 750 v./v./hr. (STP) in contact with mixed oxides catalysts consisting of 40Cr2O31OBeO-50AlzO3 prepared by digesting with IHN'Os :for varying periods, using as the source'oi chromium oxide.

TABLE III Length (if-digestion period-Yield relationship Digestion Period, hrs l 2 3O Yiolli,wcight percent 38. 0 26.5 37.7 @395 49.6

8 way of illustration mane wardens o! the present inven'tionand are not "to he construed as undue limitations ether-cot. Variations of the inventirm may be-praoticed in the light of the disclosure "without departing from the spirit or-rsoop o'f'theiinveisflaion.v

1. Aapnocessaforimanufacturingecomposite alyst consisting essentially of the oxides of alum num and at least one of theonetals selected from the group consisting of. Cr, .Mo, W, U, and V, which comprises digesting, amixture of said oxides with nitric "acid; heating the digested-quixture so as to completely drythe same-and decompose any 'nitratcstherein; andiorm'ingthe resulting oxide composite into'suitable particles for contactingoperations.

"Ihe'process of claim l"'in"which"the .fomi'ine step compiiise's";hnely comminuting thenitrateifree; dried oxide imixture; "forming a mixture of the resulting hues; and compacting said mixture into particles suitable-for contacting operations,

3.1K process for manufacturing a '.com pos'ite catalystconsisting essentially of the oxides .0! 1A1 and vBe and'at least one'oxide'selected from'the group consistin gof theoxides of "Mo, .W, "U. an V, which comprises digesting a mixture :of said oxides with nitric acid, heating the digest ed mixture so as to completelydry the same and decompose any nitrates therein and forming the resulting oxide composite into suitable particles rmcontacting operations.

:4; The-process of elaimi-a "in which the forming step comprises finely comminuting and thereafter 'pelletingthe composite.

A process :Eonmanufacturing a composite oxide catalyst which comprises digesting with hi-"- tric'acida-mixture of'the oxides of Cr, and Be "in comm-muted form, the beryllium' oxi'de con- "stitutingirom 1 to 15 weight per cent of the composite catalyst; thereafter heating'the digested mixtureuso as to completely dry the 'same'and decompose any nitrates therein; and" forming the resulting oxide "composite into suitable particles dorv contacting operations.

6i A'process ior-m'anu-facturinga composite oxide catalyst which comprises preparing a mixiar-ire 'of A1203, CI2O3, and Bee in comminute'd form wherein the GrzOs amounts'to between 1-0 and 70 per cent by weight; "the Boo between 1 and 15 per cent by weight or the mixture, and A1203 comprises the balance; digesting said mixture withlHNQain'amount between 0.5mm 5 times theweishtc-of said mixture .for :a period of atileast ADJ-hours; heating the. digested mixture so "as to :dry Lharden thevsame and; decom pnseaanyn'nitrates therein; .l-and' oomminuting the hardened oxide composite.

The process of claim ifi "wherein fresh 'HN'Oa is periodically-added to the digestion mixture so as to maintain a relatively constant liquid level therein- 8. The process-of :in which the discs-- :tion of the initial mixture .is effected in the :presence of NHtNOaih amount between 0.1 and 3 times the weight ref the tfinished catalyst.

9.. .A process for manufacturing a composite oxide catalyst whichacomprisespreparing'a mixture of A1203, CrOs, ,andi BeQ in comm-inuted-form wherein the C103 amounts to between 10 and 70 per cent by weight, the Boo to between 1 and 15 per cent by weight, of the .mixture, and the A1203 comprises the balance digesting said mixture with "HNG: in amount "between 0.25 and :5 times the we'ightof said m'ixture'for aperiodofatleast 1 hour; heating the digested mixture so as to dry and harden the same and decompose any nitrates therein; and comminuting the hardened oxide composite.

10. The process of claim 9 wherein the hardened oxide composite is comminuted to pass a IOU-mesh screen, formed into a mixture, and pelleted.

11. A process for manufacturing a composite catalyst which comprises digesting a mixture of the oxides of Al and Cr with nitric acid; heating the digested mixture so as to completely dry the same and decompose any nitrates therein; and forming the resulting oxide" composite into suitable particles for contacting operations.

12. A process for manufacturing a composite oxide catalyst which comprises preparing a mixture of A1203 and CrzOs in comminuted form; digesting said mixture with nitric acid for at least 10 hours; heating the digested mixture so as to dry and harden the same and decompose any nitrates therein; and comminuting the hardened oxide composite. I

13. A process for manufacturing a composite oxide catalyst which comprises preparing a mixture of AlzCs and C1O3 in comminuted form; digesting said mixture with nitric acid for at least 1 hour; heating the digested'mixture so as to dry and harden the same and decompose any nitrates therein; and comminuting the hardened oxide composite.

14. A process for manufacturing a composite oxide catalyst which comprises preparing a mixture of A1203 and cmoa in comminuted form wherein the Cl'zOc amounts to between 10 and 70 per cent by weight of the mixture; digestin said mixture in nitric acid in an amount between 0.5 and 5 times the weight of said mixture in the presence of added NH4NO3 in an amount between 0.1 and 3 times the weight of the finished catalyst; heating the digested mixture .so as to dry and harden the same and decompose any nitrates therein; and comminuting the hardened oxide composite.

15. A process for manufacturing a composite metal oxide catalyst which comprises digesting with nitric acid a mixture of the oxides of aluminum and at least one of the metals selected from the group consisting of Cr, Mo, W, U, and V in comminuted form; thereafter heating the digested mixture so as to completely dry the same and decompose any nitrates therein; and forming the resulting oxide composite into suitable particles for contacting operations.

16. A catalyst manufactured by the process of claim 1, consisting essentially of between 10 and per cent by weight of at least one oxide from the group consisting of Cr, Mo, W, U, and V oxides and the balance aluminum oxide.

17. A catalyst manufactured by the process of claim 3 and consisting essentially of between 10 and 70 per cent by weight of at least one oxide selected from the group consisting of the oxides of Cr, Mo, W, U, and V, between 1 and 15 per cent beryllium oxide, and the balance aluminum oxide.

18. The catalyst of claim 16 consisting essentially of between 10 and 70 per cent by weight chromium oxide and the balance aluminum oxide.

19. The catalyst of claim 17 containing CI203 in crystalline form.

EMORY W. PITZER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 21,911 Frey et al Sept. 30, 1941 1,678,078 Ramage July 24, 1928 1,881,692 Krauch et a1 Oct. 11, 1932 2,403,671 Matuszak July 9, 1946 2,411,829 Hufi'man Nov. 26, 1946 2,429,361 Linn et al. Oct. 21, 1947 2,438,569 Mattox Mar. 30, 1948 2,483,929 Owen Oct. 4, 1949 FOREIGN PATENTS Number Country Date 313,426 Great Britain June 10, 1929 

1. A PROCESS FOR MANUFACTURING A COMPOSITE CATALYST CONSISTING ESSENTIALLY OF THE OXIDES OF ALUMINUM AND AT LEAST ONE OF THE METALS SELECTED FROM THE GROUP CONSISTING OF CR, MO, W, U, AND V, WHICH COMPRISES DIGESTING A MIXTURE OF SAID OXIDES WITH NITRIC ACID, HEATING THE DIGESTED MIXTURE SO AS TO COMPLETELY DRY THE SAME AND DECOMPOSE ANY NITRATES THEREIN; AND FORMING THE RESULTING OXIDE COMPOSITE INTO SUITABLE PARTICLES FOR CONTACTING OPERATIONS.
 16. A CATALYST MANUFACTURED BY THE PROCESS OF CLAIM 1, CONSISTING ESSENTIALLY OF BETWEEN 10 AND 70 PER CENT BY WEIGHT OF AT LEAST ONE OXIDE FROM THE GROUP CONSISTING OF CR, MO, W, U, AND V OXIDES AND THE BALANCE ALUMINUM OXIDE. 